A cardiac stimulus device is a medical device, such as an implantable cardiac pacemaker or an implantable cardioverter defibrillator (ICD), for stimulating a heart with an electric signal. Some cardiac stimulus devices are surgically implanted within a patient. An implantable cardiac stimulus device includes a pulse generator and one or more electrical leads with one or more electrodes that conduct signals to and receive signals from the patient's heart. These lead(s) and their electrode(s) are placed in or proximate to the heart such that an electrical signal between electrodes is capable of stimulating the heart. The electrodes may be configured either to produce or pace an electrical cardiac event, or to detect or sense an intrinsic electrical cardiac event. Some medical devices record or otherwise collect these cardiac events. A programming device or programmer communicates with the medical device through a communication link. One example of a communication link is a telemetry link that provides means for commands and data to be non-invasively transmitted and received between the programmer and the device.
The leads of the cardiac stimulus device are connected to the pulse generator using a connector assembly or header. The connector assembly includes a lead connector and a connector cavity for the electrical and mechanical connection of the lead to the pulse generator. An IS-1 header standard has been developed as a design standard for connector assemblies. If cardiac stimulus devices from different manufacturers are designed according to the header standard, a physician has the flexibility to use one manufacturer's leads with another manufacturer's pulse generator.
The electrodes are capable of electrically sensing cardiovascular parameters. For example, the electrodes are capable of sensing intracardiac electrical activity, i.e. intrinsic electrical cardiac events. However, there are difficulties in sensing non-electrical activity or in otherwise providing additional non-electrical sensing capabilities. One of these difficulties involves encapsulation, which is the process that occurs when a foreign body enters the human body. The encapsulation of a sensor is sometimes referred to as biofouling. The immune system of the human body recognizes the foreign body and tries to reject it by building a layer of tissue around the foreign body to protect the rest of the body. Because steroids slow down the encapsulation process, steroid-eluting pacing leads have been developed.
Another difficulty in providing additional sensing capabilities for the lead involves the addition of sensor(s) on the lead. Conventionally, supporting sensor electronics are located in the pulse generator, and electrical conductors are provided between the supporting sensor electronics and the additional sensor(s). These extra conductors require more connections between the lead and the pulse generator, or can, of the cardiac stimulus device, and thus mandate a special header design that violates the header standard. That is, the cardiac stimulus device with the extra sensing capabilities has a special connector assembly and can only be used with special lead(s) that have been designed for the special connector assembly. However, physicians often desire to use one manufacturer's pulse generator with another manufacturer's lead for a number of reasons. These reasons include familiarity, the capabilities of the pulse generator, the capabilities of the leads, cost, quality, and overall flexibility in treating individual patients. As a result, the cardiac stimulus device with the extra sensing capabilities is less marketable because the special header design prevents a physician from mixing and matching leads and pulse generators.
Therefore, there is a need in the art to provide a system and method for providing additional sensing capabilities on a cardiac stimulus device lead without violating header standards.